الفهرس 
Tolerance of commercial maize hybrids to high plant density
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Abstract
Growing maize (Zea mays L.) at high-plant density using proper genotypes that withstand high density stress is a new approach to maximize its grain productivity. The objectives of the present study were to identify the optimum plant density that maximize the grain yield/fed (GYPF) of the Egyptian maize hybrids, assess the effects of plant density (PD), genotype (G) and G{u00D7}PD interaction on maize traits, estimate the superiority of tolerant (T) to sensitive (S) hybrids, estimate phenotypic (PCV) and genotypic (GCV) coefficients of variability, heritability (h2b) and genetic advance (GA) from selection for maize traits under elevated plant density and identify selection criteria for density tolerance. A set of 28 Egyptian commercial hybrids of maize, were evaluated in the field under four plant densities using a split plot design with three replications in two years. Increasing PD from 20,000 (D1) to 30,000 (D2), 40,000 (D3) and 50,000 (D4) plants/fed caused a significant reduction in grain yield/plant (GYPP), ears/plant (EPP), kernels/plant (KPP), kernels/row (KPR), rows/ear (RPE), 100-kernel weight (100-KW), leaf angle (LANG), chlorophyll concentration index (CCI), penetrated light at ear (PLE) and bottom (PLB), upper stem diameter (SDU) , lower stem diameter (SDL), ear leaf area (ELA), leaf area to produce 1g grain (LA/1gG), but caused a significant increase in GYPF, plant height (PH), ear height (EH), leaf area index (LAI), days to anthesis (DTA) and days to silking (DTS)